Pneumothorax, while easily treatable, can become life threatening if not detected at any early stage. Current methods for diagnosing pneumothorax (chest x-ray, chest CT scan) are not possible for emergency squads and not practical for long-term monitoring of critical care patients. A portable handheld pneumothorax detector that is inexpensive, accurate, and non-invasive therefore would be very attractive. In Phase I, we investigated the feasibility of such a device, based on micropower impulse radar (MIR) technology. In animal studies (swine model), we are determined that pneumothorax as small as 30 ml were clearly detectable by the MIR device. This level of detection is important for the feasibility, since it is below the threshold of clinical significance. In Phase II, we propose to further optimize the MIR characteristics of the device and the signal algorithms. We will then acquire scans on human subjects to confirm the correlation of the MIR measure to the chest x-ray, which is the present standard of care. After finalizing the device parameters, we will continue with device development, miniaturization, and packaging. This research will result in a design ready for commercialization that fulfills the need for a non- invasive pneumothorax detector. PROPOSED COMMERCIAL APPLICATIONS: A handheld inexpensive pneumothorax will be commercially attractive to emergency medical personnel and trauma clinicians. Also, it would be useful for patient monitoring in critical care units. The combined market for these applications if very large. With further development, the device may be tunable to detect other trauma conditions, such as hemotoma and hemorrhagic stroke.